Control of a Cryogenic Process Using a Fuzzy PID Scheduler

Abstract A fuzzy gain scheduling control strategy is developed that controls the temperature in a liquid helium cryostat. The behaviour of the system has a strong dependence on the operating temperature and is highly non-linear. The process operation is partitioned into fuzzy operating regions and, within each region, a linear PID controller is used to control the process. A method of relating the choice of the PID parameters to the open-loop characteristics of the system is explained. Experimental results are presented that show how the fuzzy scheduler performs in practice.